Lutetium yttrium oxyorthosilicate ((Lu1-xYx)2SiO5,LYSO,x=0,5,10,15,40)polycrystalline powders were synthesized by sol-gel method at low temperature,and their crystal structures were investigated by means of x-ray powder diffraction measurements.Unit cell parameters were determined by Rietveld refinement of the collected x-ray diffraction powder spectra.By comparison with the JCPDS card of the compounds Lu2SiO5,we propose that these LYSO solid solution structures adopt the C2/c space group symmetry.The lattice parameters and the unit cell volume slightly increases with increasing Y content.